Agronomic and chemical characterization of potential green manure species in western Kenya
1999
Ojiem, J.O. (Kenya Agricultural Research Institute, Kakamega (Kenya)) | Ransom, J.K. (Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Nairobi (Kenya)) | Odongo, O.M. | Okwuosa, E.A. (Kenya Agricultural Research Institute, Kakamega (Kenya))
Low and declining soil fertility is responsible for the low and declining level of productivity of smallholder farms in Western Kenya. Inorganic fertilizers can restore fertility of the soil, but this option is often inappropriate due to limited access to cash by farmers. Soils In Western Kenya are often def1clent In N and raising their productivity requires significant N input Legumes that fix atmospheric N can contribute to soil N supply. However, the use of legumes in soil fertility Improvement is constrained by several biophysical and socio- economic factors. Crotalaria ochreleuca, C. grahamiana, C. incana, Canavalia ensiformls, Desmodium uncinatum. Glycine max, Mucuna pruriens and Vicia villosa, were screened for biomass production and N, lignin and polyphenolic concentration, In Kakamega, Western Kenya, In 1997. Biomass accumulation ranged from 2.0 t/ha (G. max) to 9.0 t/ha (C. ochreleuca). Shoot N concentration was highest in Glycine max (variety "Nyala") (3.7%) and lowest in Crotalaria ochreleuca (2.7%), representing an N accumulation of 74 and 243 kg N/ha, respectively. Lignin concentration was lower than 15% In all species, while polyphenois were below 4%. These data indicate that there are several green manures adapted to western Kenya that cannot be exploited to improve N status of soils. All species have the capacity to decompose rapidly, releasing sufficient N to meet the demand by most cereal crops.
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